Here are my thoughts as first time player in 2007, and then maxing a normie and an ironman in OSRS, in no particular order:

0. Runelite.

1. Set your own goal(s) and then figure out your own way to them. You can only play/learn a game for the first time once, you have a precious gift. Spoiling it with roadmap guides is a sin imo. That's not to say don't look things up, some of the game can be counterintuitive or complicated, but doing your own macro theorycrafting is a lot of the fun, and uncovering content organically for the first time is a great experience.

2. OSRS has one of, if not the, best game wikis out there.

3. Try out things; find the things you like by giving everything a fair shot and making up your own mind. There are so many ways to skin a cat in OSRS, each path very diverse from others. The wiki lists so any different ways of training each skill and each of them appeal to different players.

4. Enter content with the right mindset, especially for quests. There have been several times where I've revisited a method I noped out of in the first hour on my normie but found that I quite enjoyed it the second time round on the iron. Having the right IRL mood or time constraints is a big factor for what content is enjoyable, so try as many as you can, assess the vibe and apply your toolkit accordingly.

Quests usually get a bad rep because players usually encounter them by "I want to do x, but quest y is blocking me, so now I will do 30 minutes of resentful questing before grinding x content for 50 hours". Thinking about quests as their own experience rather than an inconvenience to overcome makes them a lot more enjoyable. The lore of the world is pretty great (most of the time), the dialogue is pretty funny (most of the time). It's worth slowing down for them and enjoying them.

5. Not a tip per se but: there is a LOT of content in this game, like, an obscene amount. I'm in a clan with 50+ very degen (10+ hours a day easily with some accounts over 10,000 hours) gamers, and I'd still be willing to put money on the fact that there is content that none of us have tried. Exploring "dead" content can be a lot of fun.